Validation of Real-Time Three-Dimensional Echocardiography for

Journal of the American College of Cardiology
© 2000 by the American College of Cardiology
Published by Elsevier Science Inc.
Vol. 36, No. 3, 2000
ISSN 0735-1097/00/$20.00
PII S0735-1097(00)00793-2
Validation of Real-Time Three-Dimensional
Echocardiography for Quantifying Left
Ventricular Volumes in the Presence of a Left
Ventricular Aneurysm: In Vitro and In Vivo Studies
Jian Xin Qin, MD, Michael Jones, MD, Takahiro Shiota, MD, PHD, FACC, Neil L. Greenberg, PHD,
Hiroyuki Tsujino, MS, Michael S. Firstenberg, MD, Pankaj C. Gupta, BA, Arthur D. Zetts,
Yong Xu, MD, Jing Ping Sun, MD, Lisa A. Cardon, RDCS, Jill A. Odabashian, Scott D. Flamm, MD,
Richard D. White, MD, Julio A. Panza, MD, FACC, James D. Thomas, MD, FACC
Cleveland, Ohio and Bethesda, Maryland
To validate the accuracy of real-time three-dimensional echocardiography (RT3DE) for
quantifying aneurysmal left ventricular (LV) volumes.
BACKGROUND Conventional two-dimensional echocardiography (2DE) has limitations when applied for
quantification of LV volumes in patients with LV aneurysms.
METHODS
Seven aneurysmal balloons, 15 sheep (5 with chronic LV aneurysms and 10 without LV
aneurysms) during 60 different hemodynamic conditions and 29 patients (13 with chronic LV
aneurysms and 16 with normal LV) underwent RT3DE and 2DE. Electromagnetic flow
meters and magnetic resonance imaging (MRI) served as reference standards in the animals
and in the patients, respectively. Rotated apical six-plane method with multiplanar Simpson’s
rule and apical biplane Simpson’s rule were used to determine LV volumes by RT3DE and
2DE, respectively.
RESULTS
Both RT3DE and 2DE correlated well with actual volumes for aneurysmal balloons.
However, a significantly smaller mean difference (MD) was found between RT3DE and
actual volumes (Ϫ7 ml for RT3DE vs. 22 ml for 2DE, p ϭ 0.0002). Excellent correlation and
agreement between RT3DE and electromagnetic flow meters for LV stroke volumes for
animals with aneurysms were observed, while 2DE showed lesser correlation and agreement
(r ϭ 0.97, MD ϭ Ϫ1.0 ml vs. r ϭ 0.76, MD ϭ 4.4 ml). In patients with LV aneurysms,
better correlation and agreement between RT3DE and MRI for LV volumes were obtained
(r ϭ 0.99, MD ϭ Ϫ28 ml) than between 2DE and MRI (r ϭ 0.91, MD ϭ Ϫ49 ml).
CONCLUSIONS For geometrically asymmetric LVs associated with ventricular aneurysms, RT3DE can
accurately quantify LV volumes. (J Am Coll Cardiol 2000;36:900 –7) © 2000 by the
American College of Cardiology
OBJECTIVES
Reliable quantification of left ventricular (LV) volumes and
ejection fractions (EF) is important for serial assessment of
LV remodeling after myocardial infarction (1,2), for consideration of surgical aneurysmectomy (3–5) and for predicting long-term outcome. Currently, two-dimensional
echocardiography (2DE) using the biplane Simpson’s
method of volume determination is the most common
noninvasive tool used for the evaluation of LV volumes, but
it is limited by assumptions about LV cavity geometry (5,6).
A variety of three-dimensional echocardiographic systems
have been developed with the goal of addressing issues
about the geometric assumptions required by 2DE. By
spatially and temporally registering sequential images,
three-dimensional echocardiography has been reported to
From the Cardiovascular Imaging Center, Department of Cardiology, the Cleveland Clinic Foundation, Cleveland, Ohio; Laboratory of Animal Surgery and
Medicine, and Cardiology Branch, National Heart, Lung and Blood Institute,
National Institutes of Health, Bethesda, Maryland. This study was supported, in part,
by grant NCC9-60, National Aeronautics and Space Administration, Houston,
Texas, and grant #9951522v from the American Heart Association Ohio Local
Chapter, Columbus, Ohio, and grant #ROI-HL 56688-01A1 from the National
Institutes of Health, Bethesda, Maryland.
Manuscript received September 30, 1999; revised manuscript received March 7,
2000, accepted April 14, 2000.
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be valuable for evaluating asymmetric LV volumes and LV
function, particularly in patients with LV aneurysms (7–11).
However, these previously described methods require complex computer and echocardiographic analysis systems, carefully timed electrocardiogram/respiratory gating and prolonged imaging times (7–11). Because of these technical
complexities, widespread clinical application has been limited. Recently, a real-time three-dimensional echocardiography (RT3DE) volume scanning technique has been developed to overcome these limitations in routine clinical
settings (12–14). However, the application of this new
technology for accurate quantification of LV volumes in the
presence of LV aneurysms has not been validated.
This study was designed to show that RT3DE is more
accurate than 2DE for the quantification of volumes in
aneurysmal LVs. To accomplish this goal, we: 1) validated
the accuracy of RT3DE for quantifying modeled aneurysmal LV volumes in vitro; 2) determined the accuracy of
RT3DE for measuring LV stroke volume (SV) compared
with electromagnetic flow meter (EM) methods in a chronic
LV aneurysm animal model; and 3) evaluated the feasibility
and accuracy of RT3DE for measuring LV volumes compared with a reference standard of magnetic resonance
Qin et al.
Validation of Real-time 3DE Volumes
JACC Vol. 36, No. 3, 2000
September 2000:900–7
Abbreviations and Acronyms
2DE
ϭ two-dimensional echocardiography
EDV
ϭ end-diastolic volume
EF
ϭ ejection fraction
EM
ϭ electromagnetic flow meter
ESV
ϭ end-systolic volume
LV
ϭ left ventricle
MD
ϭ mean difference
MRI
ϭ magnetic resonance imaging
RT3DE ϭ real-time three-dimensional
echocardiography
SV
ϭ stroke volume
imaging (MRI) in patients with and without ischemic
aneurysmal heart disease.
METHODS
In vitro study. The accuracy of RT3DE for measuring
volumes was tested in ventricular phantoms that were
constructed of two balloons. A 2 to 4 cm incision was made
in the apex of one balloon, and a second balloon was
inserted into it through the incision. Water was instilled
into the inside balloon to make the aneurysmal phantom
(Fig. 1). Seven aneurysmal LV phantoms were created
having volumes of 150 to 395 ml as determined by the
amount of water used to fill each balloon. Real-time
three-dimensional echocardiographic images of the balloons
were acquired using a RT3DE system (Volumetrics Medical Imaging Inc., Durham, North Carolina) with a
2.5 MHz phased array hand-held transducer (14 mm in
diameter). In addition, standard biplane 2DE images were
obtained through the aneurysmal sections using a conventional ultrasound machine (PowerVision, Toshiba Corp.,
Tokyo, Japan).
Animal Study
Animal preparations. Fifteen sheep (weight, 40 Ϯ 15 kg)
were studied including five sheep with chronic LV aneurysms created by left anterior diagonal coronary artery
occlusion, six sheep with chronic aortic regurgitation with
normal LV geometry and without coronary occlusion and
four normal sheep. The animals with aortic regurgitation
Figure 1. After the apex of the outside balloon was excised (dashed line),
a second balloon was inserted into it. When filled with water, this produced
a phantom apical aneurysm.
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were included so that the range of ventricular volumes, that
is, those of normal sheep and sheep with aortic regurgitation, would approximate the ventricular volumes of the
sheep with ventricular aneurysms. All of the sheep were
anesthetized with pentobarbital (30 to 50 mg/kg intravenously) and 1 to 2% isoflurane, intubated and mechanically
ventilated. A midline sternotomy was performed, the pericardium incised, and the heart was suspended in a pericardial cradle. An EM flow probe (model EP455, Carolina
Medical Electronics, Inc, King, North Carolina) was placed
around the skeletonized ascending aorta distal to the coronary ostia for measuring LV SV as a reference standard. All
operative and animal management procedures were approved by the Animal Care and Use Committee of the
National Heart, Lung and Blood Institute (14).
Experimental protocol. Four hemodynamic conditions
were obtained for each sheep and included baseline conditions, after 500 ml of blood infusion and during intravenous
nitroprusside (50 ␮g/ml) and angiotensin II (2 ␮g/ml)
infusion. Real-time three-dimensional images were acquired from the epicardial LV apex under each condition.
All RT3DE images were stored on optical discs for off-line
analysis. After each RT3DE data set acquisition, 2DE
images were obtained from apical four-chamber and twochamber views and were recorded on one-half inch VHS
videotape. Care was taken to include the largest LV cavity
and aneurysm in the RT3DE pyramidal volumetric data set
and 2DE image set for the entire cardiac cycle. Left
ventricular SV obtained by integrating the instantaneous
aortic forward flow rate measured during systole from the
EM probe was compared to simultaneously recorded
RT3DE and 2DE echocardiographic assessment of SVs.
Patient Study
Population. All patients (14 with coronary artery disease
and known LV aneurysms and 20 patients without coronary
artery disease) who underwent MRI, RT3DE and 2DE at
the Cleveland Clinic Foundation during September 1997
and March 1999 were included in this study. Average age
was 56 Ϯ 7 years old, and 23 of the 34 patients were men.
Five patients (one patient with LV aneurysm and four
patients without LV aneurysm) whose RT3DE image
qualities were too poor for quantification were subsequently
excluded.
Study protocol. After institutional review board committee approval, written informed consent was obtained from
each patient. In each patient, cardiac MRI was performed to
determine LV volume and EF and was then followed by
RT3DE and 2DE studies, each performed within 1 h of the
other.
RT3DE. Using the same RT3DE machine as in the
phantom and animal study, image data set acquisition was
performed from a transthoracic apical view with the patient
in a left decubital supine position. The entire LV volumetric
data set was acquired simultaneously including apical fourchamber views, apical two-chamber views and a series of
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Validation of Real-time 3DE Volumes
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September 2000:900–7
Figure 2. Left ventricular volume measurement by the apical six-plane method. Using as an axis of rotation the line from the apex to the center of the mitral
valve annulus, the 3D Echotech system displayed the RT3DE images as six consecutive longitudinal planes rotated 30° from each adjacent plane. The LV
cavity in each plane was traced manually, and the LV volume calculated by the multiplanar Simpson’s method. LV ϭ left ventricle; RT3DE ϭ real-time
three-dimensional echocardiography.
short axis images and was stored digitally after the highest
quality image was obtained. Care was taken to include the
entire LV cavity in the real-time pyramidal volumetric data
set during the entire cardiac cycle.
2DE. Conventional transthoracic 2DE images were obtained in the apical four-chamber view and apical twochamber view with the same machine as in the phantom and
animal studies. All of the 2DE studies were performed
immediately after RT3DE examination.
MRI. Magnetic resonance imaging was employed as a
reference standard for determining absolute LV volumes in
patients. All images were obtained with a commercially
available 1.5 Tesla whole-body scanner (Siemens Vision,
Erlangen, Germany) with a phased-array coil.
Electrocardiogram-gated localizing spin-echo sequences
were used to identify the intrinsic long axis of the heart. For
all patients, short-axis dynamic gradient-echo (“Cine”)
MRI images were started in the mitral valve plane with a
slice thickness of 8 to 10 mm. These images were manually
segmented using commercially available image analysis software (Argus, Siemens Medical Systems, Iselin, New Jersey)
using Simpson’s algorithm to determine total LV volumes,
that is, end-diastolic volume (EDV) and end-systolic volume (ESV). Ejection fraction was also calculated. All
measurements were performed by an investigator experienced in cardiac MRI analysis and without knowledge of
the RT3DE measurements.
Quantitative RT3DE and 2DE measurements. For all
RT3DE and 2DE images acquired from the animals and
patients, LV EDV, ESV, SV (EDV-ESV) and EF (SV/
EDV) were determined. The RT3DE data sets were transferred to a computer system (3D EchoTech, Echo Tech
America, Lafayette, Colorado) with a dedicated software
program that was used to display the RT3DE images and to
measure LV volumes. The computer automatically dis-
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played the dynamic RT3DE images as six apical images
with a 30° angle between each image. The LV volumes were
calculated using a series of symmetrically rotated apical six
planes as previously described (15). The cavity of the LV in
each image plane was manually traced, and the LV volume
was calculated using the multiplanar Simpson’s method
(Fig. 2). For 2DE, LV volumes were calculated using the
biplane Simpson’s method from the apical four-chamber
and two-chamber views. For all measurements, LV trabeculations and papillary muscles were carefully excluded from
the LV cavity contour.
Interobserver variability. In order to assess the effect of
observational variability on the RT3DE measurement of
LV volumes, the RT3DE images of a total of eight
hemodynamic conditions in two sheep were analyzed off
line at different times with the same computer by two
independent observers, each without knowledge of the
results obtained by the other or by EM.
Figure 3. Linear regression between RT3DE, 2DE and actual volumes in
the phantom study. RT3DE ϭ real-time three-dimensional echocardiography; 2DE ϭ two-dimensional echocardiography.
Qin et al.
Validation of Real-time 3DE Volumes
JACC Vol. 36, No. 3, 2000
September 2000:900–7
Table 1. Left Ventricular Volumes Determined by RT3DE and
2DE in the Sheep Animal Model
RT3DE
Nonaneurysm
Aneurysm
2DE
Nonaneurysm
Aneurysm
n
EDV
(ml)
ESV
(ml)
SV
(ml)
EF (%)
10
5
65 Ϯ 24
60 Ϯ 29
30 Ϯ 11
35 Ϯ 19
35 Ϯ 16
25 Ϯ 12
53 Ϯ 12
43 Ϯ 10
10
5
66 Ϯ 27
67 Ϯ 25*
31 Ϯ 14
37 Ϯ 15
36 Ϯ 16
31 Ϯ 13*
53 Ϯ 10
46 Ϯ 9
*Comparison with RT3DE, p Ͻ 0.05.
2DE ϭ two-dimensional echocardiography; EDV ϭ end-diastolic volume; EF ϭ
ejection fraction; ESV ϭ end-systolic volume; RT3DE ϭ real-time threedimensional echocardiography; SV ϭ stroke volume.
Statistical analysis. Values are expressed as mean Ϯ SD for
continuous variables. The volume correlations between
RT3DE, 2DE and actual volume in the phantom study,
between RT3DE, 2DE and EM in the animal study and
between RT3DE, 2DE and MRI in the patient study
were performed using simple linear regression analysis.
Correlation coefficients were compared after Fisher
z-transformation. Agreement between methods was evaluated using the Bland and Altman method (16). Paired
Student t tests were used to compare the difference between
methods, and a value of p Ͻ 0.05 was considered statistically
significant.
RESULTS
Phantom study. Cavity volumes, which included both
balloon body volume and aneurysm volume, as determined
by RT3DE and 2DE, correlated well with actual values:
r-values were 0.996 and 0.990, respectively (Fig. 3). How-
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ever, the average difference between the RT3DE and the
actual values was significantly smaller than that between the
2DE and the actual values (Ϫ7 Ϯ 7 ml vs. 22 Ϯ 11 ml, p ϭ
0.0002). The 2DE method significantly overestimated actual cavity volumes (304 Ϯ 79 ml for 2DE vs. 282 Ϯ 76 ml
for actual volume, p ϭ 0.001); the average percentage of
overestimation was 8 Ϯ 5%. The RT3DE method slightly
underestimated actual volumes (276 Ϯ 77 ml, p ϭ 0.04); the
average percentage of underestimation was 3 Ϯ 3%.
Experiment animal studies. Left ventricular aneurysm
formation was confirmed by both RT3DE and 2DE three
months after diagonal coronary artery occlusion in five of
the LV aneurysm sheep. Left ventricular EDV, ESV, SV
and EF measured by RT3DE and 2DE in normal sheep and
those with aortic regurgitation and LV aneurysms are
presented in Table 1. In the group without LV aneurysms,
LV SV by EM methods ranged from 10 to 66 ml (34 Ϯ
16 ml). The correlation and agreement between RT3DE
and the EM method was excellent (r ϭ 0.98, y ϭ 1.02x Ϫ
0.27, p Ͻ 0.0001). For 2DE, the correlation and agreement
between 2DE and EM was moderately good (r ϭ 0.86, y ϭ
0.92x ϩ 3.80, p Ͻ 0.001, Fig. 4).
In the LV aneurysm group, LV SV calculated by EM
ranged from 14 to 58 ml (average 26 Ϯ 11 ml). For
RT3DE, the correlation and agreement between RT3DE,
and EMs were also excellent (r ϭ 0.97, y ϭ 1.07x Ϫ 2.97,
p Ͻ 0.0001). For 2DE, only moderate correlation and
agreement were obtained between 2DE and the EM
method for LV SV (r ϭ 0.76, y ϭ 0.88x ϩ 7.61, p Ͻ 0.001,
Fig. 5).
While RT3DE showed a good agreement with EM for
Figure 4. Linear regression and analysis of agreement between RT3DE, 2DE and EM for LV SV in the animals without LV aneurysms. Open circles ϭ
data points from normal sheep; closed circles ϭ data points from sheep with aortic regurgitation. 2DE ϭ two-dimensional echocardiography; EM ϭ
electromagnetic flow meter; LV ϭ left ventricle; RT3DE ϭ real-time three-dimensional echocardiography; SV ϭ stroke volume.
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Validation of Real-time 3DE Volumes
JACC Vol. 36, No. 3, 2000
September 2000:900–7
Figure 5. Linear regression and analysis of agreement between RT3DE, 2DE and EM for LV SV in the animals with LV aneurysms. 2DE ϭ twodimensional echocardiography; EM ϭ electromagnetic flow meter; LV ϭ left ventricle; RT3DE ϭ real-time three-dimensional echocardiography; SV ϭ
stroke volume.
determination of LV SV (MD ϭ 0.4 Ϯ 2.9 ml and Ϫ1.0 Ϯ
3.4 ml, respectively, in both groups, p Ͼ 0.05), 2DE
significantly overestimated LV SV obtained by EM (MD ϭ
2.1 Ϯ 9.8 ml for sheep without LV aneurysms and 4.4 Ϯ
8.4 ml for sheep with LV aneurysms, both p Ͻ 0.001).
However, in normal sheep the agreement for LV SV
between 2DE and EM methods was not significantly
different from the agreement between RT3DE and EM
(MD ϭ 0.4 Ϯ 2.9 ml for RT3DE vs. EM; 0.4 Ϯ 3.6 ml for
2DE vs. EM, open circles in Fig. 4).
Although there was no significant difference for LV
volume measurements between RT3DE and 2DE in the
animals without LV aneurysms, 2DE significantly overestimated LV EDV by RT3DE (p Ͻ 0.05) and also tended to
overestimate LV ESV in the animals with LV aneurysms,
Table 1.
Clinical studies. Results of LV EDV, ESV and EF measurements by RT3DE, 2DE and MRI are presented in
Table 2. Compared with MRI, there were no significant
differences for LV EF calculated by RT3DE and by 2DE
both in the control and the LV aneurysm groups (p Ͼ 0.05).
However, RT3DE and 2DE significantly underestimated
LV EDV and LV ESV as determined by MRI in both
groups.
For comparison with MRI, linear regression analysis was
used to determine the correlation with RT3DE and 2DE
for the LV EDV and ESV measurements. For RT3DE,
there was excellent correlation in both the control group and
the LV aneurysm group (r ϭ 0.96, y ϭ 0.79x ϩ 7.54 ml,
n ϭ 32, p Ͻ 0.0001, for the control group; r ϭ 0.99, y ϭ
0.78x ϩ 17.4 ml, n ϭ 26, p Ͻ 0.0001, for LV aneurysm
group). Two-dimensional echocardiography correlated well
with MRI in the control group (r ϭ 0.91, y ϭ 0.64x ϩ
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11.55 ml, n ϭ 32, p Ͻ 0.0001) and in the LV aneurysm
group (r ϭ 0.91, y ϭ 0.75x ϩ 2.27, n ϭ 26, p Ͻ 0.0001).
Although both RT3DE and 2DE underestimated the LV
volumes measured by MRI, the MD between RT3DE and
MRI was significantly smaller than that obtained between
2DE and MRI (Ϫ13 Ϯ 18 ml vs. Ϫ24 Ϯ 26 ml, p ϭ
0.0002, respectively, in the control group; Ϫ28 Ϯ 25 ml vs.
Ϫ49 Ϯ 41 ml, p ϭ 0.002, respectively, in the LV aneurysm
group). The average percentage underestimation of LV
volume measured by MRI using RT3DE was significantly
less than that using 2DE (11 Ϯ 16% vs. 20 Ϯ 19%, p ϭ
0.0001 in the control group; and 11 Ϯ 11% vs. 22 Ϯ 16%,
p ϭ 0.04 in the LV aneurysm group). Overall, the LV
volume measurement correlations between RT3DE and
MRI were much better than the correlations between 2DE
and MRI.
Left ventricular SV measured by RT3DE, including
Table 2. The LV EDV, ESV and EF Determined by RT3DE,
2DE and MRI in Patients
MRI
Aneurysms
Control
RT3DE
Aneurysms
Control
2DE
Aneurysms
Control
n
EDV
(ml)
ESV (ml)
SV (ml)
EF (%)
13
16
250 Ϯ 89*
142 Ϯ 47*
159 Ϯ 83*
59 Ϯ 24*
91 Ϯ 45*
81 Ϯ 26*
39 Ϯ 18
59 Ϯ 8
13
16
214 Ϯ 68
120 Ϯ 37
138 Ϯ 65
50 Ϯ 17
76 Ϯ 37
70 Ϯ 23
38 Ϯ 18
59 Ϯ 6
13
16
193 Ϯ 78
106 Ϯ 29
117 Ϯ 62
43 Ϯ 12
77 Ϯ 45
64 Ϯ 22
40 Ϯ 17
59 Ϯ 7
*Compared with the volumes measured by RT3DE or 2DE, p Ͻ 0.01.
2DE ϭ two-dimensional echocardiography; EDV ϭ end-diastolic volume; EF ϭ
ejection fraction; ESV ϭ end-systolic volume; LV ϭ left ventricle; MRI ϭ magnetic
resonance imaging; RT3DE ϭ real-time three-dimensional echocardiography; SV ϭ
stroke volume.
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Figure 6. The correlations and agreements between RT3DE, 2DE and MRI for LV SV in patients with (open circles) and without (closed circles) LV
aneurysms. 2DE ϭ two-dimensional echocardiography; LV ϭ left ventricle; MRI ϭ magnetic resonance imaging; RT3DE ϭ real-time three-dimensional
echocardiography; SV ϭ stroke volume.
control and LV aneurysm patients, correlated and agreed
with those measured by MRI (r ϭ 0.92, y ϭ 0.77x ϩ 6.73,
MD ϭ Ϫ13 Ϯ 14 ml, p Ͻ 0.0001), but the correlation and
agreement between 2DE and MRI for LV SV were decreased (r ϭ 0.82, y ϭ 0.78x ϩ 1.60, MD ϭ Ϫ17 Ϯ 21 ml,
p Ͻ 0.001, Fig. 6).
Interobserver variability. There was a good agreement
between the two independent observers’ measurements of
RT3DE volumes (58 Ϯ 27 ml vs. 57 Ϯ 27 ml, r ϭ 0.97, p Ͻ
0.0001, MD ϭ 1.3 Ϯ 1.6 ml).
DISCUSSION
In asymmetric LVs, especially those with aneurysms secondary to previous myocardial infarctions, accurate quantification of LV volumes and LV function is important for
medical and surgical management. Although MRI, radionuclide angiography and cine ventriculography are used for
the noninvasive or invasive determination of LV volumes
and EF, these methods are expensive, time consuming,
radiation exposing and impractical if repeated evaluations of
LV function are needed (17–20). Various echocardiographic
algorithms employing conventional 2DE techniques have
been developed to determine LV volumes and EF. Because
2DE is expeditious, noninvasive, mobile and relatively
inexpensive compared with the other methods, it has
become the preferred diagnostic modality to evaluate LV
structure and function. Although 2DE can detect or exclude
LV aneurysms with a high sensitivity (93%) and specificity
(94%) (21–23), the heterogeneous geometry and function of
asymmetric ventricles makes it difficult to appreciate their
shape, volume and function (5,6). In our phantom study,
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2DE significantly overestimated the actual volumes within
aneurysmal balloons (MD ϭ 22 Ϯ 11 ml) since the sector
plane was directed through the aneurysmal part, and the
largest cavity areas were used to calculate volumes. Twodimensional echocardiography also significantly overestimated LV volumes compared with RT3DE measurements
in our animal studies. This overestimation may be attributed
to placement of the probe directly on the apex and inclusion
of the largest portion of the aneurysm in the twodimensional imaging plane.
Buck et al. (20) demonstrated the accuracy of reconstructed three-dimensional echocardiography for determining LV volumes and function in 23 patients with chronic
LV aneurysms. They obtained dynamic three-dimensional
echocardiographic image data sets from a transthoracic
apical view using a rotating probe with acquisition gated to
control for electrocardiogram and respiration variation. In
their study, LV volumes were calculated from the threedimensional echocardiographic data sets by summating the
volumes of multiple short axis parallel disks. When compared with MRI, their results showed excellent correlation
and agreement for LV EDV (r ϭ 0.97, SEE ϭ 14.7 ml), for
ESV (r ϭ 0.97, SEE ϭ 12.4 ml) and for EF (r ϭ 0.74,
SEE ϭ 5.6%) and a better correlation and agreement than
that obtained with two-dimensional techniques. However,
these three-dimensional echocardiographic reconstruction
methods are technically complicated and time-consuming
(prolonged image acquisition and reconstruction time);
therefore, clinical use has been limited.
Compared with the reconstruction techniques of previously described three-dimensional echocardiographic methods, RT3DE has retained many of the clinical advantages of
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Validation of Real-time 3DE Volumes
2DE. On-line adjustment of conventional echocardiographic planes can be performed to ensure adequate quality
three-dimensional data sets. Once the entire LV was included in the RT3DE data sets, the apical aneurysm present
could be displayed by six rotated apical long axis planes. The
quantification of LV volumes can be performed quickly
when using the apical six-plane method instead of using
traditional short axis views (a series of C-scans) (15,24). In
addition, since the RT3DE hand-held probe is similar to
that of the transthoracic 2DE probe, sonographers do not
need extraordinary expertise for acquiring RT3DE data sets,
a major advantage over the previously reported reconstruction methods of three-dimensional echocardiography (7–
11,25). Another advantage of RT3DE imaging is the
elimination of the need for electrocardiogram or respiratory
gating. These factors are particularly important for studying
critically ill patients, for acquiring epicardial RT3DE images in the operation room and for imaging patients with
arrhythmias (24).
Study limitations. The limited pyramidal angle and low
frame rate of current RT3DE may be major factors for the
volume underestimation in patients. In patients with dilated
hearts, the 60° ϫ 60° pyramidal angle often limits the ability
to image the entire ventricle. We have shown in our initial
study and in this study that RT3DE significantly underestimated LV volumes when compared with MRI in patients
with severely dilated ventricles (24). Inadequate resolution
of the LV endocardium because of the mitral valve apparatus and low lateral resolution of the RT3DE images may
explain this underestimation. Also contributing to this is the
MRI technique itself, by which endocardial tracing tends to
include LV trabeculations, whereas they are excluded by
2DE and RT3DE.
The maximal achievable frame rate is only 20 frames per
second at an image depth of 14 cm. Low frame rates may be
problematic for capturing precise end-diastolic and endsystolic frames, especially in the presence of tachycardia.
This imprecision is another reason for RT3DE underestimation of LV volumes, especially LV EDV under clinical
conditions.
Conclusions. Real-time three-dimensional echocardiography showed excellent correlation and agreement with actual
volumes in a phantom study, for LV SV versus EM in a
chronic LV aneurysm animal model and for absolute LV
volumes versus MRI in patients with known LV aneurysms.
These correlations and agreements were better than those
obtained by conventional 2DE. Our results demonstrate the
feasibility and validate the accuracy of RT3DE for the
clinical assessment of patients with asymmetric LVs.
Acknowledgment
We acknowledge the assistance of the veterinary professional and technical staff of the Laboratory of Animal
Medicine and Surgery, National Heart, Lung and Blood
Institute, National Institutes of Health.
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JACC Vol. 36, No. 3, 2000
September 2000:900–7
Reprint requests and correspondence: Dr. Takahiro Shiota,
Department of Cardiology/Desk F 15, The Cleveland Clinic
Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195.
E-mail:shiotat@ccf.org.
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